1. Field of the Invention
The invention relates to a process for controlling the storage of data received by a seismic recording system and a device for implementing same.
More particularly, the process of the invention applies to the recording of seismic signals transmitted from a plurality of reception assemblies spaced apart along a seismic profile, in the form of series of digitized samples centralized in a recording and processing laboratory.
2. Description of the Prior Art
Such reception assemblies are generally formed from acquisition devices adapted for sampling the signals picked up by one or more seismic sensors, in response to echoes from subterranean layers of seismic waves emitted in the ground, for digitizing these signals and storing them. When the acquisition of these seismic signals is finished, the whole of the digital samples stored by each of the acquisition devices is transmitted to the central laboratory. The transmission may be provided either by a RF wave link or by a common cable connecting the acquisition devices in parallel.
On reception of specific control signals sent from the laboratory, each device proceeds with transmitting the data it has acquired by radio wave link or else by connecting itself to the common cable. Such an assembly is described for example in the French Pat. No. 2 511 772 or the French Pat. No. 2 538 561.
Each acquisition device causes the transmission of the data it has memorized to be preceded by identification signals. The transmission of the data may therefore be complete or split up. In the first case, all the digital words of the series are transmitted in the form of a chain. In the second case, the whole of the samples is divided into groups of samples transmitted in the form of a chain and synchronization words are transmitted between any two successive groups. When the quality of the connection is not perfect, transmission errors occur. Some digital words or groups of digital words are not transmitted or else are truncated or made indetectable because parasitic signals are superimposed on seismic data on the cable or the radio wave link. When the transmission of the series is finished, it is always possible to check whether the number of samples centralized in a storage in the central laboratory corresponds to the number of samples which were transmitted but, should a certain part thereof be missing because of transmission faults, it is impossible to know accurately at what moment the errors occurred. With the samples stored in the memory in the order of arrival thereof, some of them which did not follow each other in the transmitted series find themselves juxtaposed in the memory because some data is missing and the times in the sequence when such "packing" occurred cannot be determined.